1. Field of the Invention
Embodiments disclosed herein relate generally to fluids for use in reducing the migration of native fines in a formation towards the wellbore and subsequent plugging of pores. In particular, embodiments disclosed herein relate to kaolinite fines migration inhibition agents in wellbore fluids and methods for their use in wellbore operations.
2. Background Art
Hydrocarbon fluids, such as oil and natural gas, and other desirable formation fluids are obtained from a subterranean geologic formation, i.e., a reservoir, by drilling a well that penetrates the formation zone that contains the desired fluid. It is desirable to maximize the rate of production and the overall amount of hydrocarbon flow from the formation to the surface. One of the factors that influence the rate of hydrocarbon production is the permeability of the formation. The permeability of the formation depends on rock type, pore size, and internal capillaries in the formation. Any constriction in the capillaries or blockage of the pores will cause a reduction in the permeability of the formation and thus reduce the rate of hydrocarbon production.
Pore blockage may result from native fines migration through the formation. Specifically, native fines migration results from both fluid and hydrocarbon movement through the formation. Native fines are most likely to migrate by flowing with the phase that wets them. While some fines are found to be water-wet and thus migrate when a mobile water phase is present, others are oil-wet and flow with a hydrocarbon stream. Such fines migration often results in formation damage due to the fines plugging pores, blocking flow paths, and inhibiting potential production from the well.
Formation damage can result from several different factors, including mechanisms resulting from the nature of a reservoir and from production from that reservoir. The most difficult mechanisms to prevent are those caused by a combination of the two. These mechanisms can be considered “natural” and affect productivity regardless of the presence of drilling and completion fluids. Early treatment of natural formation damage is critical as it is extremely expensive to solve remedially with post production chemical floods. Natural formation damage, for example, results from organic and inorganic precipitation resulting from a reduction of pressure in the near wellbore region or the migration of native fines towards the wellbore and subsequent plugging of pores and blockage of flow paths. In particular, migration of kaolinite fines reduces well productivity by causing particles suspended in the production fluid to plug pores near the wellbore.
Kaolinite is typically described as hydrous aluminum silicate clay with an extended sheet structure which can be regarded as having two constituents, a layer of tetrahedral SiO4 and a layer of octahedral OH−. A significant development in the study of treating kaolinite migration in formations was the realization that oil flow causes the most significant kaolinite migration because the kaolinite fines are mixed to oil-wet. Kaolinite has a very high surface area compared to its volume, and thus is easily migrated through the pore network by flowing with the phase that wets it. Further, fine particles tend to remain in the phase that wets them. This explains why kaolinite clay is seen to migrate to oil flow. Kaolinite has an unusual wettability distribution due to the two wettability environments on the mineral surface, thus making migration prevention complex. Because the near wellbore area sees the highest flow rates during production, this area is most sensitive to velocity induced kaolinite formation damage.
Previous attempts and known methods of solving the problem of fines migration have included remediative methods such as the reverse pumping of oil back into the formation as well as treating the formation with an acid solution adapted to dissolve the fines. These attempts, however, are remediative and thus result in inefficient production from the well and excessive downtime costs.
Accordingly, there exists a need for a preventative treatment that effectively minimizes formation damage due to fines migration without the downtime costs associated with the conventional remediative treatments.